f(x)=x^2 +8x f(d-3) basically what we get from this is that the x value is d-3 to find f(d-3) simply plug in d-3 for every x f(d-3)=(d-3)^2 + 8(d-3) that would be one form of the answer, but we can also continue multiplying it out f(d-3)= d^2-6d+9+8d-24 add like terms f(d-3)=d^2+2d-15
